Drop support for dir-locals.nix, <nixpkgs>, etc.

In the spirit of Marie Kondo, I'm tidying up!

TL;DR:
- Prefer .envrc `use_nix` and delete all dir-locals.nix files
- Remove ~all references to <nixpkgs>, <unstable>, <depot> and prefer
  referencing each with briefcase.third_party.{pkgs,unstable,depot}
- Delete nixBufferFromShell function since I was only using that in
  dir-locals.nix files

2 files changed, 6 insertions, 8 deletions

diff --git a/haskell-file/.envrc b/haskell-file/.envrc
new file mode 100644
index 000000000000..a4a62da526d3
--- /dev/null
+++ b/haskell-file/.envrc
@@ -0,0 +1,2 @@
+source_up
+use_nix
diff --git a/haskell-file/shell.nix b/haskell-file/shell.nix
index f2621d6eac5a..4d5b412a0884 100644
--- a/haskell-file/shell.nix
+++ b/haskell-file/shell.nix
@@ -1,9 +1,5 @@
-with import <nixpkgs> {};
-
-stdenv.mkDerivation {
-  name = "f-hs";
-  buildInputs = [
-    (pkgs.haskellPackages.ghcWithPackages (pkgs: [
-    ]))
-  ];
+let
+  briefcase = import <briefcase> {};
+in briefcase.buildHaskell.shell {
+  deps = hpkgs: [];
 }